Laravel - Serve API requests with translated validation rules

Consider building a mobile app (or a website) which connects to a Laravel CMS over API for dynamic content. Now, the app can be a multi-language app which expects to receive a translated content from the CMS.
Usually, in our company, we instruct our frontend developers to send a lang query param on every request in order to deliver the correct translated content back.

E.g.:

GET /api/blogs?lang=en

However, Laravel validation is not aware of this and it always returns validation error messages according to app locale (or fallback locale).

Therefore we created a route middleware which groups all API routes and sets app locale based on the lang query param:

<?php

namespace App\Http\Middleware;

use Closure;
use Illuminate\Http\Request;
use Symfony\Component\HttpFoundation\Response;

class ChangeLocale
{
    /**
     * Handle an incoming request.
     */
    public function handle(Request $request, Closure $next): Response
    {
        $locale = $request->query('lang');

        if ($locale) {
            app()->setLocale($locale);
        }

        return $next($request);
    }
}

And in routes file:

// routes/api.php

use App\Http\Middleware\ChangeLocale;
use Illuminate\Support\Facades\Route;

Route::middleware(ChangeLocale::class)->group(function (): void {
    // ROUTES
});

Now your validation messages will be in the requested locale. If you don't like handling this over query param you can always use a header or something else, e.g.:

$locale = $request->header('Accept-Language');

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